1. Field of the Invention
The present invention relates to a magnetic disc drive and, in particular, to a positioning mechanism for read/write heads in a recording/playback system in which magnetic discs are utilized for information storage media.
2. Prior Art
FIG. 1 shows a conventional magnetic disc drive as disclosed in Japanese Patent Public Disclosure (Kokai) No. 59-58670 in the Official Gazette of 1984. In the drawing are shown a magnetic disc 1; a spindle motor 2 for rotating the magnetic disc 1; a magnetic head 3 for reading and writing information as electric signals to and from the magnetic disc 1; an arm 4 capable of swinging about a pivot 5, on which the head 3 is secured; a capstan 6; a stepping motor 7 directly coupled to the capstan 6 for driving the arm 4 through a steel belt 8; and a spring 9 for providing the steel belt 8 with a fixed tension.
An operation of the conventional drive will next be explained.
The magnetic disc 1 is rotated by the spindle motor 2 at the speed of, for example, 3,600 r.p.m.
The capstan 6 is rotated by the stepping motor 7 so that the driving power of the stepping motor 7 is decelerately transmitted to the arm 4 through the steel belt 8 to which a predetermined tension is provided by the spring 9. is positioned at a predetermined position on the magnetic disc 1. In such a manner, the magnetic head 3 can write information onto the magnetic disc or can read out the stored information therefrom.
However, since the conventional head positioning mechanism is constructed as described above, in a magnetic disc drive having a frame of restricted size it is not possible to allow the magnetic head 3 to have an effectively and relatively large radius of swing. Assuming that an attempt were made to obtain a desired capability by putting the angle (hereinafter referred to as a "YAW" angle) between a tangent of tracks for reading/writing information on the magnetic disc 1 and the main axis (or moving direction) of the magnetic head 3 within certain tolerance limits, for example, below 8 degrees, it might have been impossible to utilize an inner zone around the center of the magnetic disc. Thus, since only the outer zone of the magnetic disc is available for use, a disadvantage or problem has been experienced in that the memory capacity per disc must be correspondingly reduced.